Please I need help. My Volvo s80 is moving very slow and it seems not to be functioning well. Mechanic told me to change some few things in the car like the oil filter because it was dripping oil and speed sensor, spark plugs and temperature sensor. I did all that and the car was good as I thought but now, after a month or so to be precise just yesterday 17/08/2015,my car started driving with great effort but slow gear one seem like two and two like three.please can some one tell me what's the problem is? I really love the car the comfort is cool.